1. Field of the Invention
Embodiments of the invention relate to an organic light emitting diode (OLED) display capable of preventing a local light emission due to a damage of a display panel.
2. Discussion of the Related Art
Various flat panel displays whose weight and size are smaller than cathode ray tubes have been recently developed. Examples of the flat panel displays include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an electroluminescence device.
Because the PDP has a simple structure and is manufactured through a simple process, the PDP has been considered as a display device having characteristics such as lightness in weight and thin profile and providing the large-sized screen. However, the PDP has disadvantages such as low light emitting efficiency, low luminance, and high power consumption. A thin film transistor (TFT) LCD using a TFT as a switching element is the most widely used flat panel display. However, because the TFT LCD is not a self-emission display, the TFT LCD has a narrow viewing angle and a low response speed. The electroluminescence device is classified into an inorganic light emitting diode display and an organic light emitting diode (OLED) display depending on a material of an emitting layer. Because the OLED display is a self-emission display, the OLED display has characteristics such as a fast response speed, a high light emitting efficiency, a high luminance, and a wide viewing angle.
The OLED display, as shown in FIG. 1, includes an organic light emitting diode. The organic light emitting diode includes organic compound layers between an anode electrode and a cathode electrode. The organic compound layers include a hole injection layer HIL, a hole transport layer HTL, an emitting layer EML, an electron transport layer ETL, and an electron injection layer EIL.
When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the hole transport layer HTL and electrons passing through the electron transport layer ETL move to the emitting layer EML and form an exciton. Hence, the emitting layer EML generates visible light.
In the OLED display, pixels each including the above-described organic light emitting diode are arranged in a matrix format, and a brightness of the pixels selected by a scan pulse is controlled depending on a gray level of video data. In the OLED display, the pixel is selected by selectively turning on a TFT used as an active element and remains in a light emitting state due to a voltage charged to a storage capacitor.
In the OLED display, a power integrated circuit (IC) generates the driving voltage (for example, a high potential driving voltage and a low potential driving voltage) applied to the pixels and is controlled by a power control signal received from a driver IC. Even if a display panel of the OLED display is damaged, the OLED display may partially emit light because of a normal operation of the driver IC. In other words, if the driver IC normally operates in a state of the damage of the display panel, the power IC applies the driving voltage to the pixels in response to the power control signal from the driver IC. Hence, a non-damage portion of the display panel locally emits light. As described above, if only the non-damage portion of the display panel continuously emits light in an abnormal driving state such as the damage of the display panel, it is more likely to cause security problems because of local burning.
However, because the related art OLED display dose not have an element that monitors defects such as the damage of the display panel and prevents the local light emission in the abnormal driving state, it is difficult to previously prevent the security problems.